Piping installed in various plants and used for transferring fluids such as a liquid, powder, and gas has a structure in which an outer surface of a steel-made pipe body is covered with a heat insulating material (lagging material) and a protective iron sheet in order.
As a technique to inspect abnormality of the pipe body such as damage, deterioration, and fluid leakage, many methods to directly insert inspection equipment into an inside of the pipe body and perform an inspection have been conventionally proposed. However, in the methods to perform an inspection from the inside of the pipe body, it is difficult to find occurrence positions of corrosion and damage occurring on the outer surface of the pipe body, and of pipe wall thinning, holes, and cracks due to the corrosion and damage, and the existence or non-existence of fluid leakage.
Especially, it is difficult to directly visually observe and find the abnormality that occurs on the pipe body covered with the lagging material and the like. Therefore, methods to indirectly detect the abnormality from an outside using change of the humidity and the amount of moisture as a clue have been proposed.
For example, Patent Literature 1 (Japanese Patent Application Laid-Open No. 08-285717) proposes a system in which a humidity sensor is provided in a rapture-assumed position of piping, and which detects leakage at an initial stage of the leakage.
Patent Literature 2 (Japanese Patent Application Laid-Open No. 10-292893) proposes a water leakage detection device provided with a water leakage saucer outside piping, and which detects accumulated water leakage.
Patent Literature 3 (Japanese Patent Publication No. 4763632) proposes a method of measuring the moisture contained in the lagging material in which a neutron moisture meter is arranged outside piping.
The piping is arranged in a position where a worker cannot easily approach, such as a high place or a narrow place. Further, the worker may not be able to come close to the piping in order to avoid risk of radiation exposure, and a work time in the vicinity of the piping may be restricted, in a piping facility of a nuclear power station and the like.
As a technique to non-destructively inspect (flaw detection) the piping in a position where the worker cannot approach, Patent Literature 4 (Japanese Patent Application Laid-Open No. 2006-184029) proposes a method to extend an inspection arm from a self-propelled robot that travels on the ground to access the piping.
Patent Literature 5 (Japanese Patent Application Laid-Open No. 2006-126022) proposes a method to operate the inspection arm by hand.
However, the method to access and inspect the piping from the ground may be restricted due to arrangement of other structural objects in the vicinity of the piping to be inspected or risk of the work environment, and the like, and in this case, the techniques disclosed in Patent Literatures 4 and 5 cannot handle the inspection.
Therefore, the inventor of the present invention has proposed a self-propelled robot that perform an inspection using the piping itself as a supporting body, as Patent Literature 6 (Japanese Patent Application Laid-Open No. 2010-203525).
However, an inspection cart described in Patent Literature 6 is self-propelled in a state of being installed on an upper half of cylindrical piping and detects only the upper half of the piping, and is self-propelled in a state of being installed on a lower half of the piping and detects only the lower half of the piping. Therefore, it is necessary to individually inspect the piping by dividing a predetermined length range into the upper half and the lower half, and thus workability of the inspection and inspection efficiency are low.
That is, when inspecting a lower portion of the outer surface of the piping, a device body as a heavy load including a neutron moisture meter becomes in a state of being hung on the lower portion of the piping using only the arm, and thus it is necessary to enhance the strength of the arm. Therefore, it is necessary to configure configuration parts such as a traveling device in a complicated and strong manner, and the heavy load at the piping side becomes large and an operation needs time.